Ammonium pentachloromonoaquorhodate(III) is useful in photographic chemistry. A small amount of rhodium as a soluble species remain in solution after synthesis. Most of the soluble rhodium values are present as the aforementioned ammonium complex; however there are traces of the cis and trans isomers of ammonium tetrachlorodiaquorhodate(III), and traces of the fac and/or mer isomers of rhodium(III) chloride triaquo complexes are present in the process liquors from which the ammonium pentachloromonoaquorhodate(III) is precipitated.
Rhodium compounds are expensive: and therefore, recovery rather than discharge in an effluent, is desired. Furthermore, recovery is also desirable from an environmental viewpoint. Therefore, need exists for a method to conveniently recover rhodium values from the process liquor. This invention satisfies that need.
The following references disclose the Cs.sub.2 RhCl.sub.5 (H.sub.2 O) product produced by the process of this invention: Ferguson et al., Australian J. Chem., No. 7, 30, (July 1977), pp. 1445-1460, Thomas et al., J. Coord. Chem. 1973, 2 pp. 231-234, Prokofersa et al., Koord. Khim., 4, No. 1, (1978), pp.32-34. These references do not disclose the process of the invention.
U.S. Pat. No. 3,531,289 discloses a use of ammonium hexachlororhodate. Also U.S. Pat. Nos. 2,448,060, 2,566,245, 2,566,263, 4,477,561, 4,857,450; Australian 134,725; German Offen. 2,226,877; and Japan 59/171,947 relate to uses of alkali metal rhodium compounds in photographic emulsions.